Fused silica has found wide spread use as a capillary tubing material for gas chromatography applications and in glass on glass optical waveguide fibers. Practical arrangements for fixing fused silica capillaries and fibers to other silica containing components in equipment has presented a number of challenges. For example direct melt bonding of fine fused silica components to relatively larger silica supporting structures has caused unacceptable deformation or not provided adequate structural strength.
The construction of spiral-wound capillary assemblies for gas chromatography exemplifies the problems associated with joining fused silica capillary tubing to a support structure. The arrangement is fully described in copending application U.S. Ser. No. 08/394,127, filed on Feb. 24, 1995, the contents of which are hereby incorporated by reference, and uses a fused quartz mandrel to support multiple windings of fused silica capillary tubes about the mandrel. A connection communicates an end of the capillary tube with metallic tubing via a fused silica body joined to the mandrel. Contact of the capillary tube with the mandrel and simultaneous or subsequent heating did not provide enough bonding to prevent ready peeling of the capillary windings from the mandrel.
The attachment of connections to thin capillary tubing has also proven difficult. U.S. Ser. No. 08/545,080 filed on Oct. 19, 1995, the contents of which are hereby incorporated by reference, discloses a connector arrangement for withdrawing gases from the previously described arrangement of capillary tubing attached to the mandrel. The high heat capacity of the mandrel relative to the small capillary tubing causes ordinary melt bonding to again result in excessive deformation of the capillary and the fused silica body of the connection or the mandrel.
Therefore improved methods are sought for bonding the silica containing materials of the mandrel, capillary and connector body.